I have found that, even with extra calcium on the side, eggs had thinner shells while on Flock Raiser.. When my birds are young, I feed a starter, then a grower/ finisher (18% protein is plenty for teenage growing birds). Then when the pullets start laying I feed half and half grower/finisher and layer feed, until everyone is an adult. Then I go to just layer. Too high calcium levels are the biggest risk for roosters (and pullets) while they are growing and forming their bone structure. High calcium in non-laying birds does increase the risk for some calcium-related issues, but many, many roosters eat layer feed their whole adult life without any issues.
Birds do not always necessarily need higher protein. While higher protein levels may be helpful at certain times, such as during laying ( which layer ration is balanced to provide, along with extra calcium for egg shells) and molting (when less calcium is needed), protein above what is needed is simply turned into fat and stored away. Since protein is an expensive ingredient, feeding a higher protein diet increases your expenses.
Birds do not always necessarily need higher protein. While higher protein levels may be helpful at certain times, such as during laying ( which layer ration is balanced to provide, along with extra calcium for egg shells) and molting (when less calcium is needed), protein above what is needed is simply turned into fat and stored away. Since protein is an expensive ingredient, feeding a higher protein diet increases your expenses.